1. Field
Example embodiments of the inventive concepts relate to a photomask used in fabrication of semiconductor devices, and more particularly, to a reflective photomask blank used in an extreme ultraviolet (EUV) photolithography process, a reflective photomask, and an integrated circuit (IC) device manufactured by using the reflective photomask.
2. Related Art
Recently, as design rules of semiconductor devices have been drastically shrinking, the wavelength of light used in an exposure process is also decreasing. Thus, EUV that has a short wavelength has been used in the exposure process. Recently, active research has been underway into a technology for transferring a pattern onto a wafer by using a reflective exposure system including a reflective EUV photomask.
Because the wavelength used in EUV lithography may be absorbed by most materials, unlike a light exposure process using an ArF wavelength or a KrF wavelength, an EUV photomask may not use a pellicle to protect the EUV photomask. Thus, the EUV photomask is vulnerable to contamination, and also has a high possibility of contamination by carbon (C), which is a by-product of a process due to the high energy of the EUV. Accordingly, the EUV photomask requires a periodical cleaning process. Moreover, there is a need to develop a photomask having a structure in which the photomask is not damaged even when exposed to a repeated exposure process and cleaning process and is able to maintain a desired level of reflectivity, thereby having an increased lifetime.